Refractory inorganic polymers can be made at ambient temperatures and pressures. These materials include alumino-silicates or stoichiometric “geopolymers”, alkali activated cements and materials, phosphates, and other chemically bonded inorganic compounds. The use of waste products such as fly ash or slag, or components derived from biological materials as starting compounds or as reinforcements in composites demonstrates the eco-friendly and sustainable nature of these materials. Novel potential applications of such composites include fire and corrosion resistant materials, infrastructure and construction materials, thermal insulation, porous materials, structural ceramic composites containing ceramic, metal or biological reinforcements, hydrogen storage, liquid and water purification, porous materials for CO2 sequestration. The nanoparticulate nature of geopolymers also provides a low energy processing route to ultra-refractory ceramic powders such as SiC, Si3N4.